The minimization of blood loss represents a significant clinical need in the arena of surgery, trauma, and emergency response medicine. Fibrinogen is our body's native polymer system activated in response to tissue and vasculature injury, and forms the foundation of the most widely employed surgical sealant and hemostatic agent. Non-covalent knob:hole interactions are central to the assembly of fibrin that leads to network and clot formation. This project exploits these affinity interactions as a strategy to direct fibrin polymerization dynamics and network structure so as to develop a temperature-triggered polymerizing fibrin mixture for surgical applications. Short peptides modeled after fibrin knob sequences have been shown to alter fibrin matrix structure by competing with native fibrin knobs for binding to the available holes on fibrinogen and fibrin. The fusion of such knob peptides to a non-native component should facilitate binding of the fused component to fibrinogen/fibrin, and may permit the concomitant modification of the fibrin matrix. We examined this hypothesis in a three-step approach involving (a) analyzing the ability of tetrapeptide knob sequences to confer fibrin(ogen) affinity on a non-fibrin protein, (b) investigating the effect of knob display architecture on fibrin(ogen) structure, and (c) designing a temperature-responsive knob-displaying construct to modulate fibrin(ogen) affinity at different temperature regimes, thus altering fibrin(ogen) structure.

Fibrin is the body's natural provisional matrix activated in response to vascular injury in which noncovalent knob:hole interactions between fibrin monomers lead to the assembly of fibrin for clot formation. In this study we aimed to exploit fibrin knob:hole affinity interactions with swelling, space filling microgels for the development of a potential bio-synthetic hybrid polymer system with hemostatic properties. Previous work has explored the inherent binding interactions of various fibrin knobs and their complementary polymerization holes, which have led to the development of fibrin knob peptide mimic (GPRPFPAC) with enhanced binding affinity for fibrin(ogen) holes. By coupling this enhanced fibrinogen binding peptide with a pNIPAm microgel system capable of being dynamically tuned and self-assembled, we hypothesized the specific and rapidly triggered formation of a bulk hydrogel in a wound environment (i.e. in the presence of fibrinogen). We found that at the peptide ligand density and concentrations of microgels used, that a rapid formation of a gel did not occur in the presence of fibrinogen alone. However with fibrinogen and thrombin, we found that fibrin network polymerization, structure, and viscoelastic properties were greatly altered in the presence of knob peptide-conjugated microgels.

Made available in DSpace on 2014-06-11T19:23:40Z (GMT). No. of bitstreams: 0 Previous issue date: 2004-12-17Bitstream added on 2014-06-13T20:50:50Z : No. of bitstreams: 1 almeidajunior_p_me_araca.pdf: 2659878 bytes, checksum: 7b05cfcaf4408ab253ef351ae3eb5826 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A hemorragia após extração dental constitui-se em uma das complicações mais freqüentes na prática da cirurgia oral. Devido à dificuldade para se exercer manobras como pinçamentos e ligaduras de vasos neste tipo de hemorragias, existe a possibilidade do preenchimento do alvéolo com materiais hemostáticos de ação tópica. O propósito deste estudo foi analisar a influência de três hemostáticos tópicos (Hemostop®, Pro Tape® e ViscoStat®) na cronologia do processo de reparo em feridas de extração dental por meio de uma análise histológica e histométrica. Para tanto foram utilizados 60 ratos (Wistar) machos divididos em quatro grupos de 15 animais cada. Todos os animais foram submetidos à extração do incisivo central superior direito, seguido ou não da colocação de agente hemostático entre o terço médio e apical do alvéolo dental, e posterior sutura com fio reabsorvível. Em grupos de cinco, os animais foram sacrificados aos 7, 14 e 28 dias pós-operatórios por inalação excessiva de éter sulfúrico. Suas maxilas foram separadas, fixadas em formalina, descalcificadas em EDTA e incluídas em parafina. Foram realizados cortes de 6 æm de espessura e corados com Hematoxilina e Eosina, e Tricrômio de Masson. Após a análise histológica, em microscópio óptico; e histometria óssea, com o software ImageLab, os resultados foram submetidos ao teste não-paramétrico de Kruskal-Wallis. Pela metodologia aplicada foi possível concluir que: 1) houve atraso na cronologia do processo de reparo alveolar em todos os grupos tratados; 2) os materiais analisados provocaram intensa reação inflamatória no tecido adjacente; 3) em todos os períodos estudados (7, 14 e 28 dias), a análise histométrica revelou maior neoformação óssea nos animais do grupo 1 (controle). No entanto, a análise estatística constatou diferença significante (p<0,05) somente no 70 dia,... / The hemorrhage after dental extraction is one of the most frequent complications in practice of the oral surgery. Due to the difficulty to exercise maneuvers as arrestty and ligature of blood vessel in this type of hemorrhages, exists the possibility of the filling of the alveolus with hemostatics materials of topical action. The purpose of this study was to analyze the influence of three topical hemostatics (Hemostop®, Pro Tape® and ViscoStat®) in the chronology of the repair process in wounds of dental extraction through a histologic and histometric analysis. For such, 60 male's rats (Wistar) were used divided in four groups of 15 animals each. All the animals were submitted to the extraction of the right superior central incisor, followed or not of the placement of hemostatics agent among the medium and apical third of the dental alveolus, and subsequent suture with reabsorble filament. In groups of five, the animals were sacrificed to the 7, 14 and 28 postoperative days by excessive inhalation of sulfuric ether. Your maxillaries were separate, fixed in formalin solution, decalcified in EDTA and included in paraffin. Cuts of 6 æm of thickness were accomplished and stained with hematoxylin and eosin, and Masson's trichromic. After the histologic analysis, in optical microscope; and histometric bony, with the software ImageLab, the results were submitted to the no-parametric test of Kruskal-Wallis. For the applied methodology it was possible conclude that: 1) there was delay in the chronology of the alveolar repair process in all the treated groups; 2) the analyzed materials instigated a intense inflammatory reaction in the adjacent tissue; 3) in all the studied periods (7, 14 and 28 days), the histometric analysis revealed larger bony neoformation in the animals of the group 1 (control group)...(Complete abstract click electronic access below)